Mold coating



Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE MOLD COATING James a. cm; and Charles w. Swan-tout, Kenmore, N. Y., assignors to The Linde Air Products E Company, a corporation of Ohio No Drawing. Application September so, 1939, Serial No. 297.304

11 Claims.

The need for,'and theadvantages of, a protec-' tive coating over a mold surface in contact with a cast material has long been recognized in the metal and other arts employing casting and molding processes, and a great variety of substances and compositions have been proposed for this purpose. Carbon in various forms, either alone or in admixture with other materials, has been of prominentuse for mold coating purposes, and deposition of carbon fllms by applying smoky flames of acetylene or other.

hydrocarbons has produced very satisfactory results in many industries. The finely divided soot particles so deposited form a dense and uniform film which produces a better finish on the molded article, and the improvedheat insulating characteristics of such a coating maintain a better fluid flow of molten material to all parts of the mold, with improvement in the casting surface and detail. These and other advantages,

whereby the coating has greater adhesion to the mold surface with increased permanency and durability. Another object is to improve the toughness and permanency of the carbon fllm,

thereby economically providing a more uniform-. ly satisfactory finish on casting surfaces.

In accordance with the invention we propose to use a binder material in conjunction with the smoke producing flame, said binder being applied in liquid form to the mold surface and decomposed or burned thereon by the heat of the flame from which the carbon film is deposited.

Suitable binding mediums include oils or materials of oily nature, such as the higher organic acids, which upon partial combustion will leave a gummy residue on the mold surface tenacious- 1y binding the deposited carbon film.- The liquid binder can beapplied by brushing or spraying immediately prior to contacting the carbon depositing flame with. the mold surface, or the flame'may be applied both before and after wetting the surface with oil. In a third, and pre- 8 ferred, procedure an oil binder spray is applied simultaneously with the application of the acetylene or other flame, as the best mold coating is obtained by burning the binder liquid coincidentally with the carbon soot deposition. It 10 is essential to proper adherence, by any of the methods indicated, that the carbon be deposited before the binder is entirely decomposed and that the binder liquid ultimately be burned sufllciently to. produce an apparently dry, hard coat- 1 ing.

Acetylene is preferred for producing the sooty deposit and no special technique is required over that shown in the prior art to accomplish satisfactory smoking. Acetylene, burned in the at- 20 mosphere from a hand torch or other apparatus under pressures varying from about 3 to 15 pounds per square inch, vis usually employed for this purpose, with the flame adjusted so that the luminous part strikes the mold. In this 25 manner the incandescent carbon particles are chilled and condensed on the mold surface, forming the carbon deposit without noticeable escape of smoke into the air. The liquid binder can be applied simultaneously with the carbon deposition, by any suitable means, such as by aspiration under the pressure of the acetylene gas, or by a separate spray head under compressed air. The particular apparatus employed forms no part of the present invention, and the new process is operable with many apparatus embodiments which will be obvious to those skilled in the art.

As above indicated, oils andoily solutions of higher organic acids, which are decomposable 40 by heat to form a gum-like adhesive residue, are suitable binder liquids. Among the acids, oleic acid and lactic acid have shown an especially good binding action, and many oils are satisfactory in the, reflned or crude state as well as in dilution with more highly volatile components such as gasoline or benzene. Kerosene, turpentine, and linseed oil have been used successfully, and a mixture particularly preferred consists v of a good grade of light motor oil diluted some- 50 what with gasoline. The higher volatile diluent is readily vaporized by the heat of the carbon flame, and aids .in producing thinner coatings and better viscosity for spraying. The amounts of oil binder required'can be determined readily by test, and will vary with the thickness desired in the carbon coat. The oil is used sparingly, however, and in thin films which upon partial combustion will provide proper adherence without leaving an oil-wet surface. A most satisfactory coating is hard, dry and tough, resists rubbing by the finger, and is of a uniform gray appearance.

With but slight variation the process is applicable to provide improved coatings on almost any type of mold, and a wider field of use of smokeformed coatings is indicated by the present invention. Satisfactory coatings can be produced on permanent or chill molds of either cast iron or steel, cured sand molds, and some green sand molds, in the latter instance with the exercise of care to avoid destruction of the mold by the heat and force of the flame, In the casting of iron and steel, alloys, non-ferrous metals including lead, aluminum and brass, and in glass molding, the coating will serve its required func tion. The vulcanizing and curing of rubber goods, and the molding of plastics are other fields in which the invention has substantial merit. By many tests the heat insulating and mold surface protecting properties of this coating have proven to be substantially better than the carbon film formed by acetylene alone, and this provides improved. casting surfaces, and improved fineness of detail. The durability and toughness of the coating is represented by its ability to withstand several casting operations, whereas acetylene soot alone often requires renewal after each use.

Numerous modifications in the procedure described -will be evident to those skilled in the art. As a suitable binder liquid a wide scope of selection is presented, and the direct factors causing decomposition of the binder to a gumlike residue are not limiting to the invention. This has been indicated as due to a partial combustion, but a partial oxidation, polymerization, or some other action probably also occurs under the conditions of carbon deposition, and where partial combustion or burning is referred to herein, it is intended to include any associated decomposition reactions. Suitable smoking may be accomplished with gases other than acetylene, and the invention should not be limited other than as defined by the appended claims.

We claim:

l. A method of coating molds which comprises applying to the mold surface an oily liquid decomposable by heat to form a gum-like adhesive residue, and subjecting said oily liquid to partial combustion with a carbon depositing flame.

2. A method of coating molds which comprises applying to the mold surface an oily liquid decomposable by meat to form a gum-like adhesive residue, and subjecting said oily liquid to partial combustion with a carbon depositing flame of acetylene.

3. A method of coating molds which comprises applying to the mold surface an oily liquid decomposable by heat to form a, gum-like adhesive residue, and simultaneously depositing a carbon film from a smoke-producing flame adapted to effect partial combustion of said oily liquid,

4. A method of coating molds which comprises applying to the mold surface a thin film of oil decomposable by heat to form a gum-like adhesive residue, and simultaneously depositing a carbon film from an acetylene flame adapted to effect partial combustion of said oil film.

5. A method of coating molds which comprises applying to the mold surface a thin film of a liquid consisting of motor oil and gasoline, and immediately applying a carbon deposit and effecting partial combustion of said film by means of an acetylene flame.

6. A method of coating molds which comprises applying to the mold surface a thin film of a liquid consisting of motor oil and gasoline, and simultaneously applying acarbon deposit and effecting partial combustion of said film by means of an acetylene flame.

7. In a process of coating molds by smoking with an incomplete combustion flame, the steps which comprise applying to the mold surface an oily liquid capable of decomposition by heat to form a gum-like adhesive residue, and burning said liquid with said flame simultaneously with the deposition of carbon therefrom.

8. In a process of coating molds by smoking with an acetylene flame, the steps which comprise applying to the mold surface a binder liquid consisting of motor oil and gasoline and burning said liquid with said flame while depositing carbon therefrom, said steps occurring simultaneously.

-9. A mold having a tough, durable coating thereon, said coating comprising a carbon film deposited by a smoke-producing flame, and an adhesive binding said film to the mold surface, said adhesive constituting the partial combustion residue of a film of oily liquid burned by said flame while depositing the carbon coating.

10. A mold having a tough, durable coating thereon, said coating comprising a carbon film deposited by a smoke-producing flame of acetylene, and an adhesive binding said film to the mold surface, said adhesive constituting the partial combustion residue of an oil film burned by said flame while depositing the carbon coating.

11. A mold having a tough, durable coating thereon, said coating comprising a carbon film deposited by a smoke-producing flame of acetylene, and an adhesive binding said film to the mold surface, said adhesive constituting the partial combustion residue of a film of motor oil and gasoline burned by said flame while depositing the carbon coating. 4

JAMES R. CRAIG. CHARLES W. SWARTOUT.

CERTIFICATE OF CORRECTION.

Patent No. 2,256,119. March 2 19m.

7 'JAMES R. CRAIG, ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as fo'llows: Page 2, first column, line 58, claim 2, for the word "meat" read --heat--, and th'atthe said LettersPatent should be read with-this correction therein that the same may conform to the record ofthe casein the Patent Office. signed and sealed, this 29th day of April, A. 19m.

Henry Van Arsdale,

.(Sea-l) Acting Commissioner of Patents. 

